As for the method of giving water repellency to natural or synthetic fibers, there has so far been known methods of treating the fibers with silicone compounds capable of functioning as water repellent. In such a method, fibers are treated under high temperature.
Therefore, that method has a disadvantage in being subject to restrictions on the species of fiber to which it is applicable. In addition, it has defects in that it has low producibility because it requires a long treatment time and in that the water repellency is insufficient in durability.
For the purpose of diminishing such defects, there have been submitted such proposals as to apply heat to certain silicone compounds to cause cross-linking reaction therein, thereby enabling them to produce water repellency and durability (Japanese Tokko Sho Nos. 51-9440, 51-27465 and 53-4158). However, those proposals fail to ensure satisfactory water repellency and durability if the treatment is deficient in temperature and time, and so they are still insufficient for the purpose.
On the other hand, it has also been known that fluorine-containing polymers, including homopolymers of polymerizable monomers containing perfluoro or fluoroalkyl groups in their individual molecules and copolymers of said monomers and other polymerizable monomers, can produce an excellent water-repellent effect, and an antisoiling effect also, upon textile fabrics and the like even when they are used in a relatively small amount. Also, these polymers have been utilized as surface finishing agent in the fields of the leather processing industry, the manufacture of building materials and so on.
In giving water repellency or the like to textile goods, leather, building materials and so on, it is most convenient for ordinary consumers to use an agent for such a treatment in the form of aerosol spray.
In order to efficiently provide materials as cited above with water repellency by the spraying operation of an aerosol, however, various restrictions are placed on the water repellent composition.
More specifically, it is required of the composition to satisfy the following necessary conditions:
(1) a jet gas for the aerosol has high compatibility with and a good chemical affinity for a raw solution to be compounded therewith, PA1 (2) a water repellent is homogeneously dissolved in the composition, PA1 (3) when the composition is sprayed onto a material to be treated therewith, it can readily wet the surface of the material and moderately permeate thereinto, and so on.
Only when these conditions are fulfilled can the aerosol be uniformly sprayed and provide excellent water-repelling and antisoiling properties without causing a powder-coated, napping, whitening or another undesirable phenomenon.
Moreover, it is important to ordinary consumers that the water repellent composition is high in safety and free from unpleasant odor. These points are of concern as to the organic solvent incorporated in the water repellent composition.
The foregoing known fluorine-containing polymers are insoluble in alcohols of lower toxicity, such as ethanol. If the solvent is chosen from the standpoint of solubility, therefore, it can be found in the group of ketones such as acetone, methyl ethyl ketone, etc., the group of esters such as ethyl acetate, etc., the group of aliphatic hydrocarbons such as n-hexane, n-heptane, etc., the group of aromatic hydrocarbons such as toluene, xylene, etc., and the group of chlorinated hydrocarbons such as 1,1,1-trichloroethane, trichloroethylene, etc.
However, most of the above-cited solvents cannot satisfy some of the above-described conditions (1) to (3). Eventually, it is found that 1,1,1-trichloroethane alone can be used as solvent for the foregoing fluorine-containing polymers.
However, 1,1,1-trichloroethane has been lately considered a cause of destruction of the ozone layer in the atmosphere, and so the current practice is to place the use thereof under restriction from the standpoint of protecting the global environment.
Such being the case, efforts have been made to search for other solvents applicable to the foregoing fluorine-containing polymers and capable of substituting for 1,1,1-trichloroethane. However, such efforts have not yet produced satisfactory results.
On the other hand, we have made intensive studies on substitutes for the foregoing fluorine-containing polymers instead of those for the solvent. As a result, it has been found that acryl-silicone graft copolymers not only can exhibit excellent performance with respect to water repellency and an antisoiling property but also are favorable for resolving the above-described environmental problem because of their good solubility in organic solvents containing alcohols as a main component, thereby achieving the present invention.